Processes for production of pyridine 3-sulphonic acid and its salts



Patented Sept. 3, 1946 PROCESSES FOR PRODUCTIONQEP Y-RIDINE 3-SULPHONIG ACID AND I-TS SAIiTS Edmond'Ti'?Tisza andBernard F. Duesel, Yonkers, NE SE, assi-gnors to Pyridium Corporation, Yonkers; NJ Y1, incorporation of New York No; Drawing Application February- 24 194%} Seri'allNo. 4763908 40mi s;- 1; 'Our invention relates to improvements in; the. process of sulphonating, pyridine andrefers' par= ticul-arlyin processes for obtaining pyridine 3- sulphonieiacid and its salts.

While the sulphonation ofmany aromatic compoundsof" the benzene series is easily) accomplish'e'd by treating them with concentrated sul phuric acid or oleum at'relatively low temperatures, the yield, being almost quantitative; pyri dine and" its derivatives offer considerable resistance' to sulphonation" by the processes adapted for the. sulphonation of members of the benzene series: r

Numerous attempts have been made to overcome" the" difficulties present: in the sulphonation of pyridine, but they have all'resulted'ih the use ofex'cessive amounts ofthe: sulphonating compound; prolonged'heatingat highly elevatedlteniperature's' and of comparatively small yields.

The following'are among the previous attempts to sulphonate pyridine:

One process consisted in heating the pyridine with excessive proportions ofsulphuric acid and sulphuric anhydride" at 3I3O'--350 C. for sixty hours; the-sulphuric acid which was distilled'off" at these" high temperatures" being replaced from" time to time: In addition tothe large amounts of the sulphonating chemicals; and the l'ength of time employed, the yieldswereverysmall.

Attempts have been made to produce the'sulphonati'on by heating pyridine withconcentrated sulphuric acid sealed tubes to the' boilingpoint of themixture; 320'-330 0., for" thirty or"i"orty* hours without satisfactory results? Further attempts have been madeby adding a: catalyst, mercurysulpha-te; vanadiumsulphate, aluminum sulphate or. magnesium sulphate; to" the" pyridine; sulphuric a-cidand' sulphuric" anhydfii-de; heating to 330'-350" C, for'forty to sixty hours andreplacing" the distilled sulphuric acid with additional amounts of'the acid; Whileth'is" process increased the" yield above that" obtained in theabsence of the catalyst; it still possessed" the" disadvantages of the former processes" re gards". the amounts of 'sulphonatingmaterials"em ployed.

Our invention presents. processes for the pro-- duction ofipyridine3su1phonic acid in which the amountofchemicals and the time of procedure are materially decreased, and the yield is considerably increased over those of the described processes, these advantageous results being obtained by the particular steps of procedure of our processes which are not present in the prior processes.

The 'sulphonationl of. pyridine takestplacez ac cordingitoithexfollowingiormula;

It; is- 1 evidentfrom this equation :-that eachsmolj of pyridine (in; wt 79') liberates; one; mola oii wa-t ter-MB) duringsulphonationt I We have-found that .thissliberatedtwater-z dilutes the sulphuric acid to such amextent as to s-ma-ke itttooaweak for thesulphonationttoany considerable degreeand that the presence of. a dehy-edrating; agent. in sufiicient; quantity to take. up the-i water: results. in; increased; yieldst ideal, dehydrating: agent-for. thistpurpose is fuming sul-.-- phuric'; acid, it the S03 oi which formssulphuric. acid Withthe water. Using an oleumicontaining-v 20%;- S03; five-parts are required. theoretically to take care of the producediwater.

It must be considered, however; that-when; py ridinehisfi addedto the oleum,. some, 0t the-S93; Yes? capes from: the:oleum duringgthea' heating: oil the: sulphonating process and, hence; increased yields! are obtained by; employing anamount 4 in. excess. oflthetheoreticatquantityt We have now found, that we=cantincreaseithea yield of pyridine 3-sulphonic acid considerably by adding oleum tethereaction mixture at intervals. We; have: found; also that it: isiadvisable to: :add': a;.f.urther."smalhquantity 0ft: catalyst with: each a-dditiorr OfZEOlGlll'l'lL.

With. periodical: additi'onsz'oflf oleuma and? proper? catalysts we have: practically" doubled-L the yield of: pyridine 3:-sulphoni'ci aci'dc. compared: with; yields obtainedrby =theprevionsly described meth'- O'dSL- For:instance;.: using: mercuryor its-saltsas catalysts, the yield is 37'%, our yie1d is:about using: magnesiumz. as scatalyst by i the usual? method; the; yield: is: 14%,- by" our method: the:

yieldi isaw about. 23%; usings aluminum; catalyst"; by the usual method, the yield is 12i% oun yield: is about 22%.

An object of this invention, therefore,.. is to increase the? yield. of pyridine 3.-sulp'honic acid, while: at" the same .timeureducingj the'xamount of the sulphonating agent andijthe time of operation'.

Another object is to prevent the undue dilution of the sulphonating agent by the periodical addition of a dehydrating agent.

Further objects of this invention will be evident from the herein described processes and the results produced thereby.

up for the sodium salt in the usual way.

Among the catalysts suitable for application in our processes are mercury, aluminum, magnesium and vanadium and their salts, but we do not limit ourselves to these catalytic metals, as other suitable catalytic metals may be employed. These catalysts dissolve in the hot sulphuric acid as the corresponding sulphates, and therefore,

the sulphates may be added to the sulphonating mixture.

Our preferred method of sulphonation can be clearly seen from the following illustrative examples. All parts referred to in these examples are given by weights.

Example I p and 1 part of mercury sulphate are added. The

250 parts of pyridine are run as a fine stream into 750 parts of oleum (fuming sulphuric acid, S03) under stirring and cooling, taking care that the temperature does not rise over 75 C. The mixture now consists of a solution of pyridinium sulphate in oleum. Three parts of mer cury are added to the solution and heated to about 250-270 C. under constant stirring. After an hour heating 160 parts of oleum and 1.5 parts of mercury are added. The heating is continued, and after the second and third hour heating, each time the same amount of mercury and oleum is added thereto. The heating is then continued for two more hours and then cooled down to room temperature. The mixture is now added to 7500 parts of Water and neutralized with finely pulverized calcium carbonate.

The calcium sulphate formed is filtered off and washed with hot water. The filtrate now contains calcium 3-pyridine sulphonate and the unreacted pyridine, which pyridine may be recovered. Sodium or potassium carbonate is now added to the solution till it becomes alkaline to phenolphthalein, the calcium carbonate is filtered off and the solution is evaporated to dryness. By using 130'parts of sodium carbonate, 442 parts of sodium 3-pyridine sulphonate is obtained which represents 77% yield. If the free S-pyridine sulphonic acid is required, the calcium is removed from the calcium salt by the addition of the theoretical amount of sulphuric acid, the calcium sulphate is filtered off, and the solution is evaporated to dryness.

Example II A pyridinium. sulphate solution in 50 parts oleum is prepared from parts of pyridine as described in Example I. 1.5 parts of magnesium turnings are added to the solution and heated to 270300 C. part of magnesium and 16 parts oleum are added. This is repeated after the second and third hour of heating, and then the heating is continued for nine more hours. The sulphonation mixture is then cooled and added to water and worked 13.5 parts of sodium salt were obtained, representin a yield of 23.5%.

Example III A pyridinium sulphate solution in 75 parts oleum is prepared from 25 parts pyridine as de-, scribed in Example I. 1.5 parts aluminum turnings are added to the solution and heated to After heating for one hour, 0.375

Example IV A pyridinium sulphate solution in 75 parts of oleum is prepared from 25 parts pyridine as described in Example I. Two parts of mercury sulphate are added to the solution and heated to 270 C. After an hour heating 16 parts of oleum heating is continued, and the addition is repeated after an hour of heating. The heating is then continued and the reaction mixture is worked up as in Example I. The yield obtained is 68% of the theoretical.

It will be noted from the foregoing that our invention broadly comprises the periodical addition ofoleum and a catalyst to a mixture of pyridinium, oleum and a catalyst, whereby increased yields are obtained over former processes, with decreased amounts of materials and at lower temperatures.

As already mentioned other metals than those described in the examples, may be used as catalyst in the sulphonation of pyridine without departing from the invention or sacrificing the advantages thereof. Therefore, we do not limit ourselves to the specifically mentioned times, temperatures, quantities, chemicals, or steps of procedure as these are given simply to describe our invention as set forth in our specification and claims, and they may be varied without going beyond the scope of our invention.

What we claim is:

1. In a process of sulphonating pyridine in the 3 position, the step which comprises the periodical additions of oleum and a member of the group of catalysts consisting of mercury, aluminum, magnesium and vanadium and their sulphates to a solution of pyridine sulphate in oleum under sulphonating temperatures and recovering the 3 pyridine sulphonic acid.

2. In a process of sulphonating pyridine in the 3 position, the step which comprises the periodical additions of oleum and mercury to a solution of pyridine sulphate in oleum at temperatures between 250320 C. and recovering the 3 pyridine sulphonic acid.

3. In a process of sulphonating pyridine in the 3 position, the step which comprises the periodical additions of oleum and magnesium to a solution of pyridine sulphate in oleum at temperatures between 250320 C. and recovering the 3 pyridine sulphonic acid.

4. In a process of sulphonating pyridine in the 3 position, the step which comprises the periodl cal addition of oleum and mercury sulphate to a solution of pyridine sulphate in oleum at temperatures between 250-320 C. and recovering the 3 pyridine sulphonic acid. EDMOND T. TISZA.

BERNARD F. DUESEL. 

